html, body, #canvas {
    margin: 0 auto;
    height: 100%;
    overflow: hidden;
}

.bg {
    width:100%;
    background-image: url(./bg.jpg);
    height:640px;
    position:absolute;
    z-index:10;
    filter:alpha(opacity=40);
    -moz-opacity:0.4;
    opacity: 0.4;
}